One of the cases where you might need a pointer to the currently active view or document is in a modal or modeless dialog box. Generally, a dialog box should be created by the view class, because the view is what deals with the application's user interface.

Because the view class is creating the dialog box, it can pass a pointer to itself, or the active document [obtained with the GetActiveDocument() function] to the dialog box. This could be done through the dialog box's constructor or some other member function. For modal dialog boxes, the view could also put data from the dialog box into the document when DoModal() returns.

These methods are generally preferable to relying on generic functions to return pointers to the currently active view or document.

To allow you to get a pointer to the currently active document from anywhere in the program, add a static member function to your CDocument derived class as follows:

Edit the document's header file as follows to add a static member function, GetDoc():

   // Document header file

   class CMyDoc : public CDocument
   {
      ...
      public:
      static CMyDoc * GetDoc();
      ...
   };

   // SDI document implementation file

   CMyDoc * CMyDoc::GetDoc()
   {
      CFrameWnd * pFrame = (CFrameWnd *)(AfxGetApp()->m_pMainWnd);
      return (CMyDoc *) pFrame->GetActiveDocument();
   }

   CMyDoc * CMyDoc::GetDoc()
   {
      CMDIChildWnd * pChild =
          ((CMDIFrameWnd*)(AfxGetApp()->m_pMainWnd))->MDIGetActive();


      if ( !pChild )
          return NULL;

      CDocument * pDoc = pChild->GetActiveDocument();

      if ( !pDoc )
         return NULL;

      // Fail if doc is of wrong kind
      if ( ! pDoc->IsKindOf( RUNTIME_CLASS(CMyDoc) ) )
         return NULL;

      return (CMyDoc *) pDoc;
   }

Edit the view's header file as follows to add a static member function, GetView():

   // View header file
   class CMyView
   {
      
	  ...
      public:
      static CMyView * GetView();
      ...
   };

   // View implementation file

   CMyView * CMyView::GetView()
   {
      CFrameWnd * pFrame = (CFrameWnd *)(AfxGetApp()->m_pMainWnd);

      CView * pView = pFrame->GetActiveView();

      if ( !pView )
         return NULL;

      // Fail if view is of wrong kind
      // (this could occur with splitter windows, or additional
      // views on a single document

      if ( ! pView->IsKindOf( RUNTIME_CLASS(CMyView) ) )
         return NULL;

      return (CMyView *) pView;
   }

   // MDI view implementation file

   CMyView * CMyView::GetView()
   {
      CMDIChildWnd * pChild =
          ((CMDIFrameWnd*)(AfxGetApp()->m_pMainWnd))->MDIGetActive();

      if ( !pChild )
          return NULL;

      CView * pView = pChild->GetActiveView();

      if ( !pView )
         return NULL;

      // Fail if view is of wrong kind
      if ( ! pView->IsKindOf( RUNTIME_CLASS(CMyView) ) )
         return NULL;

      return (CMyView *) pView;
   }

   CMyDoc::GetDoc();

   CMyView::GetView();

Note that a pointer to the application's CDocument or CView derived class is returned, not just a generic CDocument or CView pointer. This allows you to access members specific to your new class. The MDI versions of these functions, and the SDI version of the GetView() function, will use run-time type checking to verify that the document or view is of the correct class.